1. Field of the Invention
The present invention relates to a robot control apparatus which controls a robot.
2. Description of the Related Art
In recent years, a robot system is known in which a person performs work in collaboration with a robot. In this robot system, the robot and the person perform work in a state where no safety fence is provided around the robot. A switch known as a deadman switch is disposed in a robot control apparatus. For example, when a worker presses the deadman switch at a time when the robot is to be stopped, the robot can be urgently stopped. Including the deadman switch can improve safety.
In addition, during operation of a robot, the robot sometimes comes in contact with a surrounding object or person. For example, when a person is working in collaboration with a robot, the robot may come in contact with surrounding equipment or may come in contact with a worker. In such a case, a robot system is known to control so as to detect an external force and stop the robot or perform a retreat operation for avoiding the contacted object (for example, see Japanese Patent No. 3367641, Japanese Patent No. 3459973, or Japanese Laid-open Patent Publication No. 2014-18901).
A robot is controlled so as to move along a previously produced trajectory. The trajectory of the robot can be produced based on teaching points and a speed designated by a worker. The teaching points can be set by operation of a teaching operation panel by the worker. For example, by operating the teaching operation panel, the robot is placed in a desired position and posture. The position of a tool tip point of the robot at that time can be stored as a teaching point. Then, the robot control apparatus can produce a trajectory so that the robot passes through or near the teaching point.
In a period during which teaching points are taught to the robot, the robot may frequently contact with surrounding equipment. For example, when teaching an operation of placing a workpiece on a work table, the hand of the robot is opened in a state where the workpiece is brought close to the work table. In this case, when a position for opening the hand is too high, the workpiece can be damaged. Accordingly, the position for opening the hand is preferably a position at which the workpiece is close to the work table.
The worker moves the robot up and down for adjustments in order to teach a position at which the workpiece is located slightly above the work table. When the worker is performing the operation of bringing the workpiece close to the work table, the workpiece may contact with the work table.
When the robot comes in contact with an outside object, it is preferable to cause the robot to retreat by an appropriate method. In a method of stopping a robot when the robot comes in contact with an outside object, the contact state continues and therefore the robot cannot be operated, which causes a problem in that teaching cannot be continued.
On the other hand, when the robot automatically performs a retreat operation, there is a problem in that efficiency of teaching work is deteriorated. For example, when the workpiece descends and comes in contact with the work table, control for causing the robot to automatically ascend is considered. Then, an operation of causing the robot to automatically ascend is set so as to be greatly moved in consideration of safety. Due to this, the worker needs to cause the robot to descend again to move the workpiece close to the work table. However, when the operation is not performed as desired, the workpiece may contact with the work table again. In other words, a state where the workpiece is in contact with the work table and a state where the workpiece is away therefrom may be repeated alternately. Since the worker needs to repeat the same operation, there is a problem in that teaching time becomes long.